Apparatus for the charging and discharging of storage heaters

ABSTRACT

A storage heater includes a thermally insulated double walled casing having a closed top portion surrounding a heat storage element provided with vertical air passages. The casing bottom has an air inlet and outlet whereby heated air may be circulated through the passages to heat the storage element in a first mode of operation and whereby room air can be likewise circulated to withdraw heat therefrom in a second mode of operation. A blower, positioned in a compartment having an air inlet and outlet and located beneath the casing, has its suction side in communication with the casing outlet. A pivotal flap valve near the delivery zone of the blower establishes a closed air circulation circuit through the air inlet, casing, air outlet, blower and compartment during the first mode of operation and diverts circulated air outwardly of the compartment to the exterior thereof during the second mode of operation. An electric heater is located in the compartment adjacent the delivery zone of the blower to heat the circulated air during the first mode of operation.

1221 Filed:

United States Patent 1191 Laing 1 APPARATUS FOR THE CHARGING AND DISCHARGING OF STORAGE HEATERS [76] Inventor: Nikolaus Laing, Hofener Weg 35-37, 7141 Aldingen near Stuttgart, Germany Feb. 26, 1973 21 Appl. No.: 335,780

A Related US. Application Data [63] Continuation'in-part of Ser. No. 100,341, Dec. 21, 1970, abandoned, which is a continuation of Ser. No. 778,556, Nov. 24, 1968, abandoned.

[30] Foreign Application Priority Data Nov. 27, 1967 Austria 10665/67 [51] Int. CI H05b 1/00, .F24h 7/04 [58] Field of Search 219/341, 365, 378, 219/530, 540, 325, 326, 302, 369 370, 367,

[56] References Cited UNITED STATES PATENTS 1,069,949 8/1913 Hassler 219/365 1,054,409 2/1913 Harrison et a1. 219/378 UX 2,556,498 6/1951 Jackson 219/378 2,677,243 5/1954 Telkes 219/378 UX 2,722,336 11/1955 Wexler etal. 220/15 2,776,776 l/l957 Strong et al. 220/9 3,069,045 12/1962 Haumann et a1. 220/15 THE RMUSTAT 1111 3,786,232 1451 Jan. 15, 1974 Bovenkerk 219/365 UX Rice et al..... 219/378X FOREIGN PATENTS OR APPLICATIONS 940,879 6/1948 France ....219/34l 184,467 8/1936 Switzerland ..2l9/34l Primary Examiner-A. Bartis Att0rneyWillis H. Taylor et a1.

[5 7 ABSTRACT A storage heater includes a thermally insulated double walled casing having a closed top portion surrounding a heat storage element provided with vertical air passages. The casing bottom has an air inlet and outlet whereby heated air may be circulated through the passages to heat the storage element in a, first mode of operation and whereby room air can be likewise circu-' lated to withdraw heat therefrom in a second mode of operation. A blower, positioned in a compartment having an air inlet and outlet and located beneath the casing, has its suction side in communication with the casing outlet. A pivotal flap valve near the delivery zone of the blower establishes a closed air circulation circuit through the air inlet, casing, air outlet, blower and compartment during the first mode of operation and diverts circulated air outwardly of the compartment to the exterior thereof during the second mode of operation. An electric heater is located in the compartment adjacent-the delivery zone of the blower to heat the circulated air during the first mode of operation.

7 Claims, 3 Drawing Figures PATENIEDJAH 15 I974 3, 786, 232

32 THERMOSTAT 30b J I 3/ Z5 2 35 5. 1 2.5

FIG.2 36

l APPARATUS FOR THE CHARGING AND DISCHARGING OF STORAGE HEATERS REFERENCE TO OTHER APPLICATIONS BACKGROUND OF THE INVENTION The invention relates to a storage heater with a heatable storage element comprising a heat storage mass, a thermal insulation jacket, and 'ducts which extend through the element in which a convection flow is produced by meansof a blower when the apparatus is charged or discharged.

The economic significance of storage heaters is becoming increasingly important due to the increasing availability of electric energy at low tariffs during offpeak hours and due further to the limited amount of electrical energy available during peak hours. Known off-peak current storage heaters, as for example the type illustrated in U.S. Pat. No. 3,464,486, have a storage core comprising a material of high specific heat having a capability of being heated to very high temperatures. However, owing to the excessively high temperatures of the heater core, such storage heaters necessarily must have a thick insulation to provide necessary protection which results in the heaters having large overall dimensions thus limiting their placement in rooms and making them inconvenient to install under windows. Further, any obstruction to cooling of the surface of the thick jacket by convection currents, as for example might occur if an article of clothing or paper were left on the surface of the jacket,'may result in the surface of the jacket beneath the article of clothing or paper rising to such a high temperature as to constitute a fire hazard. A still further difficulty utilizing heaters of the type having a very high temperature core is that they may not be placed close to a room wall which further limits their use as a convenient room heater. Heat storage devices having high temperature cores also generally have ambient air admixed with air leaving the core to insure that the discharge temperature of the air from the device does not exceed a predetermined limit. Such devices usually require the use of a valve which diverts some flow of ambient air through the heater core. In the event of valve failure, it is possible that all of the ambient air may be passed through the core such that the heated air discharged from the device may reach a dangerously high temperature.

Storage heaters have been proposed which utilize low temperature heater cores and which provide for charging the core with heat by recirculating heated air through the device. See for example Telkes US. Pat. No. 2,677,243. Such prior art devices however have utilized complex valve and ducting arrangements for circulation of air past the heating means and through the core area which complexity has resulted in heaters having overall large dimensions making them inappropriate for use as compact heat storage devices. Further, such storage heaters have included inlets and outlets on the sides of the casing surrounding the core which have resulted in loss of heat from the core by convection currents during a time when it is not desired to discharge heat from the storage heater.

Insulation structure has been proposed where the structure comprises inner and outer insulation walls forming a chamber where the chamber contains a gas and a porous filler material and where the pore size of the material approaches the mean free path of the gas. See for example the insulation structure shown in Bovenkerk US. Pat. No. 3,167,159. Such insulation structure has not been utilized, as far as is known, with heat storage deviceswhere one of the purposes is to ob tain a reduction in the overall size of the device as compared with conventional devices in order that they may be applicable for use as room heatersf It is an object of the invention to provide for a low temperature storage heater having a highly insulated casing structure where the heater has a small overall dimension. It is a further object of the invention to provide for a storage heater which will not lose heat through convection currents when shut off and which will provide a structure by which the complete heat storage element may be completely and evenly charged by circulating heated air past a heating means and through a closed circuit including the heat storage elements as a part of the circuit.

SUMMARY OF THE INVENTION I Broadly, a storage heater constructed according to the invention includes an insulated casing having a closed top portion which surrounds a heat storage element and where the element has a plurality of vertically extending air passages. The bottom of the casing has air inlet and air outlet means by which air may be passed into and out of the casing to pass over the storage elements to heat the same in one mode of the operation,

and to withdraw heat in another mode of the operation.

A blower compartment is positioned beneath the casing and has a blower therein, the suction part of which is in communication with the ,outlet means. A pivotal flap valve is positioned near the delivery zone of the blower and in one position serves to direct air to the inlet means of the casing to complete a closed circuit of air flowing in the casing over the heatstorage element and through the compartment, and, in another position, to divert air from the compartment to the exterior of the storage heater inv order to heat a room while ambient air is allowed to flow into the air inlet means. A heater means in included in the discharge area to heat air passing into the casing and over the storage element to charg the same.

Preferably, the'casing is thin and comprises an innerand outer wall forming a chamber which contains gas and a porous filler material having pore sizes approximating the mean free path of the gas. charge Also, preferably, the connection between the inner and outer walls of the casing adjacent the inlet and outlet means comprises a bellows-like structure which impedes flow of heat from the inner wall to the outer wall and which at the same time provides a flexible connection between the walls to compensate for differential expansion of the walls.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view of a storage heater constructed according to the invention;

FIG. 2 is a view of the heater of FIG. 1 taken along lines 2-2; and

FIG. 3 is a view of the heater of FIG. 1 taken along lines 3-3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT- Referring to FIG. 1, there is illustrated a storage heater having a storage element 32 and an insulated casing 33 surrounding the element and having a closed top portion. The storage element 32 is divided into a plurality of cylinders 37 forming air ducts 28 therebetween as shown in FIG. 3.

The insulated casing 33 has an inner wall 300 and an outer wall 301 which is spaced from the inner wall. The inner wall 300 has therein openings 302 and 303 while the outer wall has openings 304 and 305 which are oppositely disposed to the openings in the inner wall. A bellows-like member 306 joins openings 302 and 304 to form an. inlet means 24 while the openings 303 and 305 are joined by a bellows-like member 307 to form an outlet means 25. The bellows-like structure provides means to accommodate differential expansion between the inner and outer walls because of temperature differences while at the same time effectively decreases the transfer of heat from the inner to the outer wall by increasing the resistance to flowof heat.

A blower compartment is positioned beneath the casing 33 and has therein a blower 35. Blower 35 in turn is positioned beneath the outlet means 25 with its suction zone beneath the outlet and with the discharge zone extending in the compartment towards the inlet means 24. A heater means 34 in the form of an electric grid is positioned in the discharge zone.

A flap valve is pivoted at 20 in the delivery zone of the blower such that when the valve is in the open position, as shown in full lines'in FIG. 2, it will divert air from the delivery zone ofthe blower to the exterior of the device through the grating 31 into the room to be heated. When the valve 30 is in the position shown in dotted lines in FIG. 2, air from the discharge zone of the blower will flow into the inlet means 24.

The individual cylinders 37 of the heat storage element contain heat storage masses having high latent heat properties including phase change temperatures of approximately 700C. Preferably the mass is of such nature to store and give up latent heat without substantial change in temperature. Further it is preferable that conversion temperature of the mass be below the maximum permissible temperature of the insulated casing 33 and below the maximum permissible temperature of the blower which is usually on the order of 700C.

A thermostat 32' is located near the suction zone of the blower and provides a control means for turning the heater 34 on when the temperature at the outlet means is below the conversion temperature of the heat storage mass contained in the individual'cylinders 37 and to turn the heater off when the temperature of the air is above the conversion temperature.

The operation of the device is as follows. During charging, the flap valve 30 is'in a dotted line position as shown by 30' which provides a closed circuit of air from the heater 34 through the compartment, into the inlet means 24, through the passages 38, into the outlet means 25, through the blower and back to the heating means 34. The air passes over the complete length of the cylinders 37 such that all of the storage mass therein will be subjected to heating to melt the same. When the temperature at the outlet means 25 as determined by the thermostat 32 reaches a temperature which is equal to the operating temperature of the storage mass, all of the storage mass would have been melted and the heating means will be shut off. Since the casing is closed at the top and the inlet and the outlet openings are only in the bottom thereof, there can be no escape of the heat from the core and casing due to any convection currents.

When it is desired to heat a room in which the heater is placed, the flap valve is opened as shown at 30 in FIG. 2 and the blower is started. Ambient air in the room will enter through inlet grating 22 into the inlet means 24 and over the storage element picking up heat in the process, out through the outlet means 25,

through the blower and out through the discharge grating 31.

It is seen that a storage heater of the type illustrated has small overall dimensions so that it may be conveniently positioned in a room, as for example beneath a window. Since a low temperature core is utilized, there is no danger of extremely high temperatures existing on the surface of the casing or of discharge temperatures being exceedingly high so as to present any fire hazard.

It is seen further that by charging the heat storage element in the manner shown, that those zones of the element which at the beginning of the charge operation may have contained their fullheat content from a preceding charge, will receive only a slight increase of heat while those zones of the element which have given up some or all of this latent energy will be fully recharged even if they are still at the conversion temperature. This will result in all parts of the storage element ending up with substantially the same heat content since the heat mass selected preferably stores and gives up heat within a small temperature range.

This is to be distinguished from conventional heat storage devices having a storage core where a portion of the core is cooled down during discharge leaving other portions which are very hot. If discharge of such devices is terminated in this condition, the temperature of the core will tend to stabilize with those zones of the core having high residual heat content giving up energy to discharged zones until a mean temperature of the complete core is established. When such conventional devices are charged, the different zones may receive uneven heating resulting in some zones being overly heated while other zones receive only enough heat to have the mass in that zone undergo a phase conversion.

What is claimed is:

1. A storage heater comprising an insulated casing having a closed top portion, a heat storage element in said casing having a plurality of vertically extending air passages therein, a heat storage mass in said element having a phase conversion point at a conversion temperature above a predetermined discharge temperature of the device, air inlet means in the bottom of said casing, air outlet means in the bottom of said casing, a blower compartment beneath the bottom of said casing with said air inlet and air outlet means opening into said compartment, blower means in said compartment having a suction zone in communication with said outlet means and a delivery zone adapted to be in communication with said inlet means where said blower means is adapted to induce flow of air in said casing from said inlet means to said outlet means and through said compartment, heater means in said compartment in the path of air flow, and a valve for diverting flow of air from said compartment to the exterior thereof when said valve is in the open position and for allowing air to flow from said outlet to said inlet when in the retracted position to form a closed circuit of air flow in said casing and compartment.

2. A storage heater according to claim 1 wherein said heater means is positioned in the path of air flow between said blower and said inlet means.

3. A storage heater according to claim 2 wherein said valve is positioned in the path of air flow in the compartment between said heater means and said inlet means.

4. A storage heater according to claim 1' wherein said element comprises a pluralityof vertically extending cylinders of different axial lengths and wherein the spaces between adjacent cylinders form said air passages.

5. A storage heater according to claim 1 wherein said casing has an outer wall, an inner wall spaced from said outer wall and forming with said outer wall a hermetic chamber, a gas in said chamber. and a porous insulathrough the bottom of said casing. l 

1. A storage heater comprising an insulated casing having a closed top portion, a heat storage element in said casing having a plurality of vertically extending air passages therein, a heat storage mass in said element having a phase conversion point at a conversion temperature above a predetermined discharge temperature of the device, air inlet means in the bottom of said casing, air outlet means in the bottom of said casing, a blower compartment beneath the bottom of said casing with said air inlet and air outlet means opening into said compartment, blower means in said compartment having a suction zone in communication with said outlet means and a delivery zone adapted to be in communication with said inlet means where said blower means is adapted to induce flow of air in said casing from said inlet means to said outlet means and through said compartment, heater means in said compartment in the path of air flow, and a valve for diverting flow of air from said compartment to the exterior thereof when said valve is in the open position and for allowing air to flow from said outlet to said inlet when in the retracted position to form a closed circuit of air flow in said casing and compartment.
 2. A storage heater according to claim 1 wherein said heater means is positioned in the path of air flow between said blower and said inlet means.
 3. A storage heater according to claim 2 wherein said valve is positioned in the path of air flow in the compartment between said heater means and said inlet means.
 4. A storage heater according to claim 1 wherein said element comprises a plurality of vertically extending cylinders of different axial lengths and wherein the spaces between adjacent cylinders form said air passages.
 5. A storage heater according to claim 1 wherein said casing has an outer wall, an inner wall spaced from said outer wall and forming with said outer wall a hermetic chamber, a gas in said chamber, and a porous insulation material filling said chamber wherein the diameter of the pores of said material is less than the mean free path of said gas at the operating temperature of said heater.
 6. A storage heater according to claim 5 wherein the pressure within said chamber is sub-atmospheric.
 7. A storage heater according to claim 1 wherein said casing has an outer wall, an inner wall spaced from the outer wall and forming with said outer wall a hermetic chamber, and openings in the inner and outer bottom walls joined by bellows means to form an air duct through the bottom of said casing. 